The present invention relates to valves, more particularly to weir valves.
A weir valve is a valve utilizing a resilient diaphragm that engages a weir and prevents the flow of fluid over the weir. Weir valves provide excellent sealing and isolation characteristics to effectively contain the fluid being controlled and substantially eliminates leaking or migration of the controlled fluid into the valve mechanisms or out of the valve. Weir valves are also more amenable than conventional valves in designing streamlined fluid flow courses through the valves.
In many applications, particularly in the semiconductor industry, quiescent or dead spots in the fluid flow course must be avoided as these can cause the fluid to become stagnant or to degrade and contaminants or suspended solids can accumulate in the quiescent or dead spots. Any of these can cause significant quality control problems.
In many applications in the semiconductor industry it is necessary to instantaneously change fluid flow to a particular process. Additionally, need arises to alternate a particular fluid flow between different processes or equipment. This type of fluid switching can be accomplished with two two-way weir valves and an external T-connection. However, when two valves are used, the previously mentioned problems of fluid degradation or contaminant build-up are exacerbated.